Menwith Hill is the worlds largest monitoring communications station and is situated just outside Harrogate, North Yorkshire, on the edge of the Yorkshire Dales. Its official title is R.A.F Menwith Hill which is misleading since it is actually run by the US National Security Agency (NSA).

The official cover story is that it is an all-civilian base and is a Department of Defence communications station, the Ministry of Defence (MoD) describing it as a "communications relay centre".

Little is known about the true activities of the station, although the word 'spying' seems to be always associated with it. This could be due to its extensive 560 acre complex of masts, satellite dishes and radomes (affectionately called 'golf balls' by the locals) and a fibre-optic link supplied by British Telecom (BT) which has a call capacity of about 100,000 concurrent voice telephone channels (the phone bill must be horrific).

The station is subject to much controversy, recently due to the planned installation of 'Star Wars' equipment at the site. Two new radomes are to be built for the Space Based Infra Red System (SBIRS). The Campaign for the Accountability of American Bases (CAAB) claim that the installation of the equipment is unlawful under international arms control treaties.

Claims of industrial espionage with British and European Companies by the station are also common, but never been proved. Protesters allege the equipment is being used to sell information to the US and thus allowing them to have an unfair competitve advantage. Selected information is exchanged with the British listening post at the Government Communications Headquarters (GCHQ) and a number of GCHQ staff work at the station.